Please I need help. PHYSICS

Question

A car of mass 1.2 x 10¹²kg is traveling along a straight horizontal road at a speed of 20 m/s when it brakes sharply then skids.

Friction brings the car to rest.

If the coefficient of friction between the tires and road is 0.8, calculate:

a) the deceleration

b) the distance travelled by the car before it comes to rest

Answer 1

(a)

a = F/m = -μmg/m = -μg

The deceleration is the absolute value of a.

|a| = μg = 0.8(9.8 m/s²) = 7.84 m/s²

(b)

Use the kinematic relation

v² - v₀² = 2ad

v = 0

v₀ = 20 m/s

-v₀² = 2ad

d = -v₀² / (2a) = -(20)² / [2(-7.84)] meters = 25.51 meters